In a preceding project, the entrainment of respiration of vagal volleys revealed that units in certain parts of the forebrain discharged in phase with respiration. Earlier work on the present project demonstrated that units in several parts of the forebrain discharge spontaneously in phase with respiration. Because of the variation in duration of the respiratory cycle, an analysis of the data presented special statistical difficulties. In the present phase of the work a satisfactory computer-assisted statistical analysis has been achieved for the continuing work on respiration-related units.